Published ahead of print on January 31, 2003, doi:10.1165/rcmb.2002-0135OC Am. J. Respir. Cell Mol. Biol., Volume 29, Number 1, July 2003, 81-87 A more recent version of this article appeared on July 1, 2003
Submitted on July 29, 2002 Continuous Mechanical Contraction Modulates Expression of Alveolar Epithelial Cell PhenotypeJorge A Gutierrez1*,1 Pediatrics, University of California, San Francisco, San Francisco, CA, USA; Pediatrics, University of California, San Francisco, San Francisco, CA, USA, 2 Medicine, University of California, San Francisco, San Francisco, CA, USA; Cardiovascular Research Institute, University of California, San Francisco, San Francisco, CA, USA * To whom correspondence should be addressed. E-mail: jgut{at}itsa.ucsf.edu.
We have previously reported that mechanical distention of alveolar epithelial type II cells in culture favored the expression of the type I cell phenotype and inhibited the expression of the type II cell phenotype. The objective of the present study was to investigate the effects of continuous mechanical contraction on the expression of specific markers for the type I and type II cell phenotypes in cultured alveolar type II cells. Type II cells were mechanically contracted in culture at varying amplitudes and times. Cells were analyzed for mRNA and protein content of markers of the type I (RTI40) and type II (surfactant proteins A, B and C) phenotypes. Continuous contraction of culture membrane surface area by 25% for a duration of 4 hours resulted in an 83% increase in SP-A, a 42% increase in SP-B, and a 230% increase in SP-C, in comparison to controls. After 12 hours of contraction, RTI40 mRNA content decreased to 59% of control levels. A minimal contraction of 20% of culture membrane surface area was required to modulate expression of the type II cell markers. In summary, mechanical contraction favors expression of the type II cell phenotype and inhibits expression of the type I cell phenotype in a time- and amplitude-dependent manner.
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